Making cast steel railway wheels

ABSTRACT

In the cooling of a steel railway car wheel having relatively thick hub and tread portions and a relatively thin plate portion, it is important that undue stresses are not set up in the plate portion and, simultaneously, that the tread is hardened for good wear qualities while the hub is kept soft for easy machinability. These objectives are achieved by providing a conveyor having suspended thereover, at spaced intervals, non-metallic insulating disks having a diameter approximately equal to or slightly larger than the wheel hub diameter, moving the wheels in intermittent steps along the conveyor so that the wheels stop for a predetermined period of time directly under successive disks until the hubs have cooled from a temperature of about 1,700* F. to below the critical transformation temperature which is about 1,200* F., the other portions of the wheels having cooled at a faster rate.

United States Patent [191 Kucera et a1.

[451 Aug. 21, 1973 MAKING CAST STEEL RAILWAY WHEELS [75] Inventors: William James Kucera; Albert Thomas Wendt, both of Elmhurst, 111.; Louis Sandor, Hammond, lnd.

[73] Assignee: Amsted Industries, Incorporated,

Chicago, Ill.

[22] Filed: Feb. 23, 1972 [21] Appl. No.: 228,690

[52] US. Cl 148/3, 148/146, 148/148, 148/155 [51] Int. Cl C21d 1/28 [58] Field of Search 148/3, 146, 148, 148/149, 155; 266/4, 5, 6; 263/8 [56] References Cited UNITED STATES PATENTS 3,558,367 l/1971 Eek 148/3 3,043,317 7/1962 Hursen.... 266/6 X 1,859,623 5/1932 Gregg 148/149 1,071,012 8/1913 Unger 148/146 3,370,993 2/1968 Carpenter et al 148/13.1

Primary Examiner-Charles N. Lovell Attorney-Walter L. Schlegel, Jr. et a1.

[57] ABSTRACT In the cooling of a steel railway car wheel having relatively thick hub and tread portions and a relatively thin plate portion, it is important that umdue stresses are not set up in the plate portion and, simultaneously, that the tread is hardened for good wear qualities while the hub is kept soft for easy machinability. These objectives are achieved by providing a conveyor having suspended thereover, at spaced intervals, non-metallic insulating disks having a diameter approximately equal to or slightly larger than the wheel hub diameter, moving the wheels in intermittent steps along the conveyor so that the wheels stop for a predetermined period of time directly under successive disks until the hubs have cooled from a temperature of about 1,700 F. to below the critical transformation temperature which is about 1,200 F., the other portions of the wheels having cooled at a faster rate.

3 Claims, 1 Drawing Figure MAKING CAST STEEL RAILWAY WHEELS In prior art railway wheel production, cast steel wheels after removal from molds, are slowly cooled in an oven to a range of the order of l,l50-l,200 F., whereat the axle hole is cut, and the wheels are then heated in a normalizing furnace to approximately 1,700" F., and then cooled to approximately .1 ,150 F., after which the hubs are force cooled by water sprays or air jets in order to obtain proper stress patterns in the plate portion of the wheels. The disadvantage of this procedure is that, while satisfactory stress patterns are obtained, the hub is unduly hard and thus has very poor machinability.

If the entire wheels are air cooled other problems arise because the hub and tread are at approximately the same hardness. If, for example, the rate of air cooling is such as to produce a tread with good wear qualities, the hub is difficult to machine. If, on the other hand, the rate of air cooling is such as to producea machinable hub, the tread is too soft to provide good wear qualities. One method by which the problem has been overcome is that shown in US. Letters Pat. No.

3,558,367 wherein the normalized wheels are placed on insulating disks on a cooling conveyor, and a second insulating disk is placed on the upper surface of the "wheel hubs, the disks shielding only the hubs so as to retard their cooling rate as compared to the cooling rate of the wheel tread portions. This method not only required additional manpower to physically place a diskon each wheel hub,but proper cooling rates may be difficult to achieve on cooling lines of short length. In other words, such direct contact insulating disksmay function too efficiently under somecircumstances and hub temperatures may not have passed through the critical temperature range by the time the endof the cooling line is reached.

In the present arrangement a steel railway wheel is produced which has a tread sufficiently hard so as to have good wear properties while the hub is soft enough to be easily machined, while at the same time the disadvantages of prior art methods are overcome.

The method of making wheels according to this invention will be better understood with reference to the single FIGURE of the drawing. which is a crosssectional view of a railway car wheel on a cooling conveyor.

Referring to the drawing, a wheel indicated generally at 10, which preferably is cast steel containing less than one percent by weight of carbon, has a central relatively thick hub 12 and a relatively thick tread l4 interconnected by a relatively thin plate 16. The wheel is illustrated at that portion of the manufacturing cycle wherein, preferably, an axle hole 17 has been torch cut and the wheel is being transported on a conveyor indicated schematically at 18.

In the preferred method of carrying out the present invention, and by way of example, there is disclosed a method of making a cast steel railway car wheel. In this method, a cast steel wheel is removed from themold and cooled slowly to a temperature in the range of l,l F. to l,200 F., whereat an axle hole 17 is torch cut through the wheel hub section. The axle hole, of course, may be rough cut at a later point in time or may be formed by'means of a core during the casting operation. The wheel is then heated in a normalizing furnace to a temperatureof the order of 1,700 F. As the wheel emerges from the normalizing furnace, it is preferably placed upon an insulating disk 20 which is positioned on slat conveyor 18. The insulating; disk is preferably of refractory fiber glass but may be any ceramic insulating material which will withstand temperatures. of up to 1,700 F., or a fibrous insulating material such as asbestos. A pluralityof insulating disks 22 are suspended as by wires 24 at spaced intervals along the conveyor. Only one such disk is shown in the drawing but there may be twenty or more such disks spaced along the conveyor. The material of which the suspended disks 22 are made may be a refractory fiber felt with or with out a bonding agent of colloidal silica cement, a refractory fiberglass or other refractory, non-metallic insulating material which will withstand temperatures of up to l,700 F.

Although the suspended disks may be flat, they preferably are formed with a concave under-side, for example in theshape of an inverted pie tin or dish having an outer diameter of approximately one and one half times the wheel hub diameter. This preferred size and configuration has proved to more adequately control the dissipation of heat from the entire wheel hub such that the hub cools at amuch slower rate than the tread portion 14. The suspended disk shown has a wall thickness of approximately one-half inch and a height of aboutonefourth of the disk diameter.

By way of example, the normalized wheels, at a starting temperature of about 1,700 F., are moved in steps through 20 stations, the time in motion between stations being about 5 seconds and the time during which the wheels are at rest under each insulating disk is about secondsln this instance the lower rim 26 0f each disk is spaced about one-half inch above the top surface 28 of each wheel hub. One of the advantages of this method is that if either a shorter or a longer cooling line must be used, vsuspended insulating disks may be added or deleted along the line, or the spacing between the suspended disk and the hub face may be readily variedso as to-ensure that the wheel hubs have cooledslowly through the transformation temperature while the tread portion cooled at a faster rate because it had been completely exposed.

The transformation temperature will generally be approximately l,230 F. and, in practice, the hub is cooled to a temperature value within the range of at most approximately l,l50 F. to l,200 Fby the time the last suspended insulating disk in the line has been passed. The wheel isthen permitted to cool to room temperature, preferably without any force cooling by jets of air or water. The foregoing method results in wheels having a preferred tread hardness in the range of approximately 265-300 BIIN, and hub hardness less than about 240 BI-IN.

Cast steel railway wheels have been made according balance with residual impurities in ordinary amounts Iron What is claimed is: -l. A method of making a steel railway wheel, comprising the steps of: forming the steel while molten wto the shape of a wheel, then after the wheel has solidified cooling the wheel to a temperature value within a range of the order of l,250 F. to room temperature, then heating the wheel to a normalizing temperature value, then air cooling the wheel by placing it on a conveyor having suspended thereover at spaced intervals a plurality of non-metallic insulating disks having a diameter larger than the wheel hub diameter, then moving the wheel in intermittent steps along the conveyor and stopping the wheel for a predetermined period of time under successive disks until the wheel hubs have cooled half times the hub diameter.

t k k 

2. A method according to claim 1 wherein the insulating disks are provided with a generally concave portion facing the wheel hub.
 3. A method according to claim 2 wherein the insulating disks are formed of a refractory material and have an outer diameter of approximately one and one half times the hub diameter. 